The present application claims priority upon Japanese Patent Application No. 2001-282189 filed on Sep. 17, 2001, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a dot-matrix printer, and a method of printing.
2. Description of the Related Art
A representative example of a dot-matrix printer is a dot-matrix impact printer (or, a dot-impact printer). According to a dot-impact printer, a dot pattern structuring characters is formed on an image buffer of the printer based on data sent from a host such as a personal computer, and according to this dot pattern, a printing medium, such as paper, is stroke by an impact wire (or, a printing pin) to print the characters.
In a main scanning direction, there is a case where, according to a relationship between the number of dots and the number of characters to be formed on the printing medium per a unit length, an average number of dots per character does not become a natural number. For example, in a case of printing by 12 cpi (twelve characters per inch) at a dot density of 90 dpi (ninety dots per inch), in average, there will be 90÷12=7.5 dots per character on the printing medium.
However, in actuality, since the number of dots which the dot-impact printer can strike on the printing medium is a natural number, it becomes necessary to adjust the intervals between characters. For example, under the above mentioned condition of 90 dpi, 12 cpi, assume that three same characters are to be printed. A space allotted for a first character is 7 dots (1 dot for the non-character portion at the left side, 5 dots for the character portion, and 1 dot for the non-character portion at the right side); a space allotted for the second character is 8 dots (1 dot for the non-character portion at the left side, 5 dots for the character portion, and 2 dots for the non-character portion at the right side); and a space allotted for the third character is 7 dots (1 dot for the non-character portion at the left side, 5 dots for the character portion, and 1 dot for the non-character portion at the right side). Thus, spaces would have to be allotted non-uniformly.
As a result, the interval between the first character and the second character (2 dots) differs to the interval between the second character and the third character (3 dots).
Such a difference in the intervals between characters due to the relationship between the number of dots and the number of characters per unit length is not preferable from a point of view of printing quality.
If resolution of the image buffer used upon printing is increased, and dot density of printing is increased, the above situation may be avoided. For example, if the resolution of an image buffer is set at 180 per inch, and the dot-striking density with impact wires is set at 180 dpi in order to print at 12 cpi, a space allotted for one character on the printing medium becomes fifteen dots (180 dpi/12 characters). Thus, if a plurality of the same characters is printed many times, the characters may be aligned at equal intervals on the medium to be printed.
However, in the case of a dot-impact printer which prints by striking with the impact wire, in order to increase resolution of the image buffer and to increase the dot density of printing, it is necessary to decrease the size of dots and to increase the number of times to strike on the same unit area.
If impact wires are made too narrow in order to decrease the size of dots, there is fear that the strength of the impact wires decrease and the impact wires may become easy to break, or the impact wires may tear through an ink ribbon. Further, if the number of times of striking on the same unit area is increased, there is fear that the printing paper may tear. Therefore, there is naturally a limit to the narrowness of the impact wire and/or the number of times of striking, and thus, there is a case where resolution of the characters and/or dot density may not be arbitrarily increased.
The present invention has been made in view of the above and other problems, and an object of the invention is to provide a dot-matrix printer and a printing method in which characters may be uniformly arranged and printed on a to-be-printed medium even when an average number of dots per character is not a natural number, without changing the size of printing or the dot density.
In order to solve the above and other objects, one aspect of the invention is a dot-matrix printer for printing on a printing medium comprising: a dot-forming section for forming dots on said printing medium; and a referenced data section to be referred to during movement of said dot-forming section, a character string to be printed being indicated in said referenced data section as data having a predetermined resolution. In a state in which M dots per a unit length are formable on said printing medium in a moving direction of said dot-forming section, and upon printing a character string of N characters per said unit length, said M and said N both being natural numbers, if (M÷N) is not a natural number, said resolution in said moving direction is made to be a number L per said character string of N characters, said L being a least common multiple of said M and said N, and while said dot-forming section moves across said unit length, said dot-matrix printer carries out printing while referring to said referenced data section for said L times.
Further, another aspect of the present invention is a dot-matrix printer for printing on a printing medium comprising a dot-forming section for forming dots on said printing medium. In a state in which M dots per a unit length are formable on said printing medium in a moving direction of said dot-forming section, and upon printing a character string of N characters per said unit length, said M and said N both being natural numbers, said dot-matrix printer being capable of arranging said character string of N characters at equal intervals and carrying out printing, even if (M÷N) is not a natural number.
Other features of the present invention will become apparent according to the appended drawings and the disclosure of this specification.